New Atomic's 4tiX: Greater safety in lightweight ski-binding thanks to Zytel and Delrin

With an innovative design and the use of two DuPont engineering polymers, 4tiX, a new super-lightweight ski-binding by Austrian winter-sports-equipment maker Atomic, combines comfort and reliability with added safety in complex twisting falls. The two toe-clamps, which hold the front of the ski-boot and release it if the skier falls, are made of glass-reinforced Zytel nylon. The toe-piece housing, the automatic heel-release housing and a large number of other components are made of Delrin acetal.

With an innovative design and the use of two DuPont engineering polymers, 4tiX, a new super-lightweight ski-binding by Austrian winter-sports-equipment maker Atomic, combines comfort and reliability with added safety in complex twisting falls.

The two toe-clamps, which hold the front of the ski-boot and release it if the skier falls, are made of glass-reinforced Zytel nylon. The toe-piece housing, the automatic heel-release housing and a large number of other components are made of Delrin acetal. They include:

the anti-friction device (AFD in skiing parlance), which allows a virtually friction-free lateral movement of the boot's toe,
parts of the tensioning system,
parts of the ski-brake and
parts for locking the toe-piece housing in place after tensioning.
It is the properties of Zytel and Delrin which render them highly suitable for winter-sports equipment. They keep their high impact resistance and strength over the entire temperature range of –40 °C to +40 °C, they can be readily coloured in glowing colours, they produce scratch-resistant, high-quality surfaces; parts made of these engineering polymers have a low tendency to ice up.

The design of the human hip-joint, in engineering terms a ball-and-socket joint, inspired Atomic's idea for the system that holds the toe-clamps in place. Each toe-clamp is mounted on two balls, one above the other. A spring-loaded bolt pulls the balls into their respective tight-fitting sockets embedded in the housing of Delrin.

If the binding opens due to lateral forces (boot twists sideways), the clamp swings horizontally around the two joints, like a door on two hinges. If the opening force is upwards (skier falls backwards, boot lifts at front), the lower balls are forced out of their sockets and both parts of the clamp turn on a horizontal axis formed by the upper bearing points. In a backwards fall coupled with a lateral force, just one ball remains in its socket, allowing the binding to open diagonally upwards.

'The combination of Zytel for the balls and Delrin for the sockets in this bearing system ensures that the binding operates with minimal friction and wear at any temperature,' comments Franz Resch, Atomic's development manager for bindings.

'There are no squeaks and there is enough safety margin even without lubrication. Moreover, hardly any ice forms on the outer surfaces, so that even in the most unfavourable circumstances the release force is increased by only 10 percent, whereas the standard specification allows a 35 percent increase.'

He continues: 'A 4tiX binding weighs only about 1.8 kg, which is roughly 20 percent less than a conventional lightweight binding. With our innovative, yet simple design we were able to substantially reduce the number of individual parts in the whole toe-piece compared to conventional designs with their separate metal dowel pins. Fewer parts mean less manufacturing time and lower costs. And because we worked closely with DuPont from the outset, it took us only two years from the original idea to series production.'

Wolfgang Bolesta, technical consultant in DuPont's Engineering Polymers business unit, worked with Atomic during the entire development period. He notes that several other companies also helped to make this rapid development schedule possible.

'The toe-clamps of Zytel are moulded with gas-injection technology, or GIT,' says Bolesta. 'GIT produces hollow parts that are lighter and allows shorter cycle times. Stieler-Kunststoff Service, of Goslar, Germany, a GIT specialist moulder, and Günther Heißkanaltechnik, of Frankenberg, Germany, developed their own patented process, in which the melt and the gas are injected through the same injection point. The opening in the moulding is sealed during the process, so that snow and water cannot get into it.'

Bolesta continues: 'After moulding, the parts are powder-coated. Here Atomic together with DuPont and Hillebrand, of Wickede, Germany, developed a special process which locks the powder-coating securely on the nylon surface, ensuring added resistance to scratches, abrasion and impact.'

'The parts made of Delrin in the toe-piece and heel-piece housings as well as the brake-plate are also coated after moulding. For this process Atomic used know-how from Seca Plast, of Laško, Slovenia, and Hillebrand, both licensees of DuPont's Delrin Decorating Solutions system. This technology package includes the combination of plastic material, etching solution and appropriate coating materials plus counselling in application technology, and makes it possible to coat and metallise parts made of Delrin acetal resin.'

Another novelty in the winter-sports-equipment industry is the use of laser-printing to mark the DIN scale on the parts of Delrin in the release tensioning mechanism. Unlike other printing processes, laser-printing produces permanent marks.

DuPont modified the acetal resin for this process so that the laser beam creates the required high-contrast colours. ASM Maschinenbau, of Fuschl, Austria, developed the equipment to apply the laser etching, based on a high-end laser marker.

Atomic Austria GmbH is a subsidiary of AMER Sports Corporation, of Helsinki, Finland. Amer, with 6 800 employees, is one of the world's leading sports-equipment companies, with its internationally recognised brands Atomic, Wilson, Suunto, Precor and (since May 2005) Salomon. Annual turnover is € 1,7 billion. The Atomic brand produces equipment for nordic and alpine ski-ing and for snowboarding, Dynamic for alpine ski-ing, Volant for high-segment ski-ing and Oxygen for snowboarding. Atomic and Salomon together produced about 1,5 million skis for the 2005/2006 season, or about 30 % of the world market.